Actinic keratosis is a horny growth, such as a wart or callosity on the skin, generally sharpy outlined, red or skin-colored, flat or elevated, verrucous or keratotic growth, which may develop into a cutaneous horn, or may give rise to squamous cell carcinoma. It usually affects the middle-aged or elderly, especially those of fair complexion and is caused by excessive exposure to the sun.
Traditional treatments of actinic kertosis have included appliction of cytotoxic agents such as fluorouracil with or without an occlusive dressing, dissolved or suspended in an ointment, lotion, or glycol solvent applied to the affected area. The dosage schedule invariably has required an uninterrupted, once or more times daily application of the agent for at least several weeks. Penetrating solvents have been investigated for enhancing percutaneous absorption of fluorouracil in an effort to more successfully treat more resistive conditions.
Severe skin inflammation from damage to treated tissue by the cytotoxic agent typically occurs with this treatment, severely limiting its usefulness.